Field
Aspects of the present disclosure relate, in general, to position location and, more particularly, to transmitting a relative change in location from a target device to a location server for the location server to determine the absolute location of the target device.
Background
It may be beneficial to obtain the location of a mobile device such as a wireless phone, laptop, tablet, identity tag, etc. at one or more times and to provide the location to some client application or device for the purpose of supporting some service or function. Examples of services and functions include providing navigation instructions to the user of the mobile device, tracking and/or recording the location of some valuable asset, and enabling the mobile device to obtain its own location.
To support location of mobile devices that have the capability to access wireless networks such as Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Long Term Evolution (LTE) and WiFi and/or fixed access networks such as packet cable and DSL, a number of position methods and associated positioning protocols have been developed that rely on communication between the mobile device and a location server supported by one or more intervening fixed and/or wireless networks. One such positioning protocol developed by the 3rd Generation Partnership Project (3GPP) in 3GPP Technical Specification (TS) 36.355 which is publicly available is known as the LTE Positioning Protocol (LPP) and is intended to locate mobile devices that are currently accessing an LTE network.
An extension to LPP known as LPP Extensions (LPPe) is being developed by the Open Mobile Alliance (OMA) to locate mobile devices that are currently accessing an LTE network or certain other kinds of network such as GSM, WCDMA, WiFi or fixed access. The relationship of LPPe to LPP is that each LPP message is allowed to optionally include an embedded LPPe message.
The LPP, LPPe, and certain other positioning protocols, support location by having the capability to transfer assistance data from the location server to the mobile device that is being located to better enable the mobile device to make measurements of suitable signals (e.g., signals from Global Positioning System (GPS) or Global Navigation Satellite System (GNSS) satellites, signals from wireless network base stations) and, in some cases, to determine its own location from these measurements. The protocols also have the capability to allow the location server to request and later receive particular signal measurements and other location related information from the mobile device to enable the location server to calculate the location of the mobile device.
Positioning methods such as those supported by LPP and LPPe can determine a location of a target device from measurements by the target device of known external signal sources, such as GPS satellites or network base stations. In addition, measurements by network entities (e.g., base stations) of signals from the target device may also help determine the location of the target device. These measurements may enable the current absolute location of the target device to be obtained, for example its precise latitude, longitude, and altitude.
If a target device is unable to measure signals from external sources, and network entities are unable to measure enough signals from the target device, it may not be possible to obtain the location of the target device, and/or to obtain the location within a required response time or with a required accuracy. Such cases may occur when there are physical obstructions between the target device and the external signal sources and/or network entities. For example, a target device can be inside a building or tunnel, in a subway or basement, outside in a dense urban environment, or very distant from terrestrial external radio sources and network entities.